The present invention relates to a motor having a rotor of a consequent-pole structure.
For example, Japanese Laid-Open Patent Publication No. 9-327139 discloses a rotor of a consequent-pole structure as a rotor for a motor. The rotor of the above publication includes a rotor core, a plurality of magnets arranged along the circumferential direction of the rotor core, and salient poles integrally formed with the rotor core. Each salient pole is located between a circumferentially adjacent pair of the magnets. The magnets function as either north poles or south poles, and the salient poles function as magnetic poles different from the magnets. While suppressing reduction in the performance, this motor reduces the number of magnets to half of those in a conventional rotor in which all the magnetic poles are formed by magnets. The motor of the publication is therefore advantageous in terms of natural resource and cost saving.
In the meantime, since the rotor of a consequent-pole structure as in the above publication has, in a mixed state, magnets for inducing magnetic flux and salient poles, which do not induce magnetic flux, the rotor is likely to be magnetically imbalanced. As a result, the rotational performance is degraded due to vibrations increased, for example, by the occurrence of cogging torque.